Find the 20th term from the last in the sequence 3 7 11 407

331.

Series is increased by 4.
Want to find the 20th term from last means,
we want to decrease by 4 from the last to 20the term from last.

407 is last number in the sequence.
therefore,
407,403,399,395,391,387,383,379,375,371,367,363,359,355,351,347,343,339,335,(331)
12 years agoHelpfull: Yes(11) No(3)
since in A.P. last term is 407 nd first is 3,
a=3 l=407 nd d=4
now l=a+(n-1)d,
407=3+(n-1)4,
n=102 then 20 from last is eqaul to 83 from start
T83=3+(83-1)*4=331....
12 years agoHelpfull: Yes(5) No(0)
331 is the answer.
12 years agoHelpfull: Yes(4) No(1)
Difference of 7,3 is 4.
reverse the series as we need 20th number from last.
therefore, 407,403,.....11,7,3
now use the formula Tn=a+(n-1)d
a=407
d=-4(as we are have reversed the series)
n=20(as we need 20th term from 407)
Tn=407+(20-1)(-4)=> 407+19*-4 => 407-76 => 331(Ans)
11 years agoHelpfull: Yes(0) No(2)
Total number of terms in AP :
407=3+(n-1)4
n=102
Now 20th term from the last of the series will become's 83th term from the beginning of the series as (102-20+1=83)

Now simply calculate the value of 83 term ;
T=3+(83-1)*4 = 331
8 years agoHelpfull: Yes(0) No(1)

Find the 20th term from the last in the sequence 3,7,11.... 407 ?